Lawyers for Trayvon Martin's family have expressed fears that George Zimmerman, the teenager's killer, intends to escape justice by fleeing Florida.

It is unclear whether law enforcement officials know the location of Zimmerman, the self-appointed neighbourhood watch captain who claims he shot and killed the unarmed boy in self-defence during a confrontation in February.

Zimmerman's attorneys Hal Uhrig and Craig Sonner dropped the 28-year-old as a client on Tuesday, in an extraordinary press conference during which they confirmed they had never met him and did not know where he was.

Neither the Sanford police department nor the state attorney investigating the case would confirm to the Guardian on Wednesday that they knew of Zimmerman's location. It is not even clear whether he is still in Florida.

Benjamin Crump, who represents Trayvon Martin's parents, Sybrina Fulton and Tracy Martin, said he was concerned by comments from Zimmerman's former lawyers that they had lost contact with him.

"We have a lot of anxiety over the simple fact that nobody knows where the killer of Trayvon Martin is, that he is unaccounted for," Crump told CNN.

"That is a major concern because if the charges come forth like we believe they rightfully should, the question is: can they get him, to hold him accountable? Will he escape justice by fleeing? He is a flight risk right now, and we are concerned about that."

Crump welcomed an announcement by special prosecutor Angela Corey that she would hold a news conference before the end of Friday.

Corey is expected to announce her decision over whether to bring charges against Zimmerman, who told police that he fired his gun because Martin attacked him. The killing of the unarmed black teenager and Zimmerman's immediate release prompted mass protests and elevated racial tensions in the central Florida town.

A spokeswoman for Corey's office told the Guardian on Wednesday that it would not comment on Zimmerman's whereabouts until the press conference, which she said was being called to release "new information" in the case.

Inquiries to the Sanford police department, meanwhile, were being directed to Corey's staff. Police have previously said they were "in contact" with Zimmerman, "which is different from 'We know where he is'," according to John Miller, a CBS News analyst.

"It's entirely uncertain to me whether they actually do know where he is," he said.

Uhrig and Sonner said they had not heard from Zimmerman since Sunday and that he was no longer returning their calls or emails. They dropped Zimmerman as a client, they said, because he had contacted Corey's office against their advice and set up his own fundraising website outside of their guidance.

In their Tuesday press conference, the pair questioned Zimmerman's mental state, suspecting him to be "emotionally crippled" by the reaction to the case, admitted they had never had a face-to-face meeting with him and expressed their belief that he had already left Florida.

But they said they would be happy to work with him again if he got back in touch.

Zimmerman, meanwhile, has been careful to cover his tracks, online at least. His website, therealgeorgezimmerman.com, was set up through a company in Scottsdale, Arizona, that specialises in private and anonymous registrations.

With every new development in the case analysed publicly, other high-profile lawyers have been quick to offer opinions. Jose Baez, Casey Anthony's former attorney, and Mark Geragos, who represented Michael Jackson, both appeared on CNN to criticise Uhrig and Sonner.

"It's unbelievable that you would get on television and talk about your client's mental state. It's reprehensible," said Baez.

Geragos likened the press conference to a Saturday Night Live comedy sketch. "What do they have in the water down there in Florida?" he said.

"This is just absolutely the worst thing I can remember seeing any lawyer do in regards to their client. Some of the previous interviews were train wrecks, those things were toy cars compared to what this is."